1. Field of the Invention
The present invention is in the technical field of metalworking operations and lubricants used therein.
2. Description of Related Art
Lubricants are generally employed in metalworking operations. Such operations include rolling, forging, blanking, bending, stamping, drawing, cutting, punching, spinning, extruding, coining, hobbing, swaging, and the like. The present invention concerns improved lubricants for such metalworking operations, and in particular such operations as are employed in automotive and appliance applications. In the automotive and appliance fields, the term “stamping” is used as a broad term to cover all pressworking operations on sheet metal, which operations may be further categorized as cutting, drawing, or coining. Automotive and appliance stamped parts may be produced by one or a combination of these three fundamental operations.
Metalworking lubricants facilitate these operations generally by reducing friction between the metal being worked and the tooling employed for that process, and thus reducing the power required for a given operation, reducing the wear of the surfaces of the tooling that operate on the metals, and preventing sticking between the metal being worked and the tooling operating thereon or between metal pieces during storage, handling, or operations, and, in addition, often provide corrosion protection to the metal being processed. In automotive and appliance applications prevention of sticking between metal pieces and between such pieces and the work elements is of extreme importance.
In some metalworking processes, including automotive and appliance applications, coils or rolls of steel, in particular cold rolled or galvanized steel sheets, are cut into pieces, called blanks, that are stamped or drawn to produce the desired parts. Such automotive parts formed by stamping or drawing, as these terms are generally used, include fenders, hoods, deck lids, quarter panels, oil pans, fuel tanks, floor panels, inner and outer door panels, and the like. Appliance parts, formed by stamping and drawing, as these terms are generally used, include washer tops, dryer tops, washer fronts, dryer fronts, top and front lids and dryer tumblers, and the like. Prior to the use of lubricants known as prelubes, the normal procedure was to apply an oil at the steel mill to such coils or rolls as a rust preventative prior to shipping to the processing site, such as a stamping plant. Between the steps of cutting the sheets into blanks and stamping or drawing, such rust preventive oil would then be removed by cleaning and a drawing lubricant applied to the metal and at times the work element immediately before stamping or drawing. Such drawing lubricant is used to reduce friction and facilitate the metalworking operation.
In more recent times, the use of separate rust preventive oils and drawing lubricants has been in some instances replaced by the use of a single composition known as a prelube. Prelubes are generally applied at the steel mill during temper rolling or inspection, as was done with rust preventive oils, prior to shipping and are not intentionally removed from the metal until after the blanks are cut and the parts formed. Thus, the use of such prelubes eliminates the steps of removing the oil and applying a drawing lubricant before further working.
Prelubes thus must function as both a rust preventative and drawing lubricant. In many instances, and particularly for automotive and appliance applications, a prelube must be: (a) removable with alkaline cleaners, (b) non-staining to the metal, and (c) compatible with other chemicals utilized in producing the products in question.
As to metal staining, there are at times instances where steel coils are stored for long periods before use. Some substances may oxidize during storage and the oxidation product may adversely affect the metal, for example, by the oxidation of oils to fatty acids, which stain steel sheets, particularly mild steel sheets. Hence, industries in which storage periods are not uncommon require prelubes or other substances in contact with the metal during storage that are substantially non-staining. Additionally, with time these oils may be subject to attack by microorganisms yielding substances that may be detrimental to the desired properties of prelube.
Antimicrobial compositions are generally added to various kinds of industrial water based fluids to reduce or inhibit the growth of microorganisms. In particular, a wide variety of industrial water based fluids, such as metal-working fluids, latex paints, water based hydraulic fluids, require antimicrobial compositions to control the growth of microorganisms that eventually render the fluids rancid.
A number of suggestions have been made for inhibiting the growth of bacteria in aqueous fluids, such as those described in U.S. Pat. Nos. 4,172,140, 3,951,830, 3,799,876, 3,515,671, and 2,976,244. The use of various formaldehyde preservatives for metalworking fluids, including monomethylol dimethyl hydantoin and dimethylol dimethyl hydantoin, has also been proposed (see Bennett, E. O., Int. Biodetn. Bull. 9:95-100 (1973)).
Gray and Wilkinson in J. Gen. Microbiol, 39:385-399 (1965) and J. App. Bact., 28:153-164 (1965) describe the action of the ethylenediaminetetraacetic acid (EDTA) on some bacteria. The effectiveness of such chelating agents as EDTA for bacterial control in aqueous systems is disputed as evidenced by U.S. Pat. Nos. 3,240,701; 3,408,843; and 3,591,679.
U.S. Pat. No. 2,711,374 discloses a corrosion inhibiting composition that comprises a synthetic aliphatic polybasic acid ester lubricating oil that contains small proportions of oil soluble petroleum sulfonate and similar proportions of natural animal fatty material and partial ester of polyhydric alcohol. To these are added lecithin in proportions of 0.01 to about 2% in combination with 0.1 to 1% of antioxidant, preferably of the alkylated phenol type.
U.S. Pat. No. 3,313,727 discloses an EP lubricant produced by the dispersion in a nonpolar lubricating oil of an inorganic hydrated sodium or potassium borate. To prepare the lubricant, the borate, water and an emulsifier were introduced into the nonpolar medium. The mixture was then agitated to produce a microemulsion of the aqueous borate solution in the oil and thereafter heated to remove the liquid water. It is also disclosed that conventional additives, such as rust inhibitors, foam inhibitors, etc., can be present in the finished lubricating composition containing the borate.
U.S. Pat. No. 4,163,729 discloses a synergistic extreme-pressure lubricating composition comprising an oil of lubricating viscosity having dispersed therein: (1) 0.1-60 weight percent of hydrated potassium borate microparticles having a boron to potassium ratio of about 2.5 to 4.5, (2) from 0.01 to 5.0 weight percent of an antiwear agent selected from (a) a zinc dihydrocarbyl dithiophosphate having from 4 to 20 carbons in each hydrocarbyl group; (b) a C1-C20 amine salt of a dihydrocarbyl dithiophosphoric acid having from 4 to 20 carbons in each hydrocarbyl group; (c) a zinc alkyl aryl sulfonate; or (d) mixtures thereof, and (3) from 0.1 to 5 weight percent of an oil-soluble antioxidant organic sulfur compound containing from 3 to 40 weight percent sulfur, which sulfur is present as organic sulfide or polysulfide or mixtures thereof.
U.S. Pat. No. 4,846,986 discloses an oil-in-water emulsion said to be useful as a metal working lubricant. The emulsion includes water, a oil-in-water emulsifier, a film plasticizer, and a boundry lubricant. A corrosion inhibitor may also be included.
U.S. Pat. No. 4,925,582 discloses that alkane alkanolamines of the formula RNHR1OH wherein R is hydrogen or normal C1-6 alkyl; and R1 is a normal or branched chain C2-4 alkyl or hydroxymethyl C2-4 alkyl are effective to potentiate the activity of and prolong the useful life of antimicrobial agents in controlling the growth of microorganisms in industrial water based fluids. A specific example of the alkanolamines employed is n-hexyl ethanolamine.
U.S. Pat. No. 6,172,122 discloses a stable emulsion composition that comprises: (A) a metal overbased gelled composition, prepared by forming a mixture of (i) a carbonated overbased material in an oleophilic medium, which material contains a metal salt of at least one organic acid material containing at least 8 carbon atoms, and (ii) an alcohol or an alcohol-water mixture; (B) a surfactant; and (C) an aqueous liquid. The stable emulsion composition may further comprise at least one of a solute, a suspended solid, or an oxidation inhibitor.
Japanese Patent Application No. 58-106540 discloses lubricating emulsions for metalworking that contain fats, mineral oils or fatty acid esters, and extreme pressure additive, and water soluble cationic or amphoteric polymer salt dispersions containing nitrogen. Thus, a lubricant was manufactured by mixing 95 wt % tallow, 2 wt % tallow fatty acid, 1 wt % poly(diethylaminomethyl methacrylate) phosphate, 1 wt % zinc phosphate, and 1 wt % 2,6-di-tert-butyl-p-cresol.
Kane, P. and Kray, L., J. Soc. of Tribologists and Lubrication Engineers, 54(1): 15-25 (1998) reported studies on coolant degradation and the development of a laboratory test method for predicting soluble oil emulsion oxidation stability.
The disclosures of the foregoing are incorporated herein by reference in their entirety.